caisson

Noun

1. A (permanent) enclosure from which water can be expelled, in order to give access to underwater areas for engineering works etc.
   • During the construction of the viaduct, the sinking of the caissons in the river bed caused much difficulty to the engineer and contractors, as a bed of running sand was encountered; in consequence, the expenditure for...
   • Caissons were enclosed dry chambers built on river beds to facilitate the construction of bridge piers. - 2003, Bill Bryson, A Short History of Nearly Everything, BCA, page 213:

   Coordinate Terms: cofferdam coffer

2. A structure with similar function that is temporary.

   Synonyms: cofferdam coffer

3. A coffer (sunken panel).
4. The gate across the entrance to a drydock.
5. A floating tank that can be submerged, attached to an underwater object and then pumped out to lift the object by buoyancy.
   • Near-synonym: pontoon

   Synonyms: camel sea camel pontoon

6. A two-wheeled, horse-drawn military vehicle used to carry ammunition (and a coffin at funerals).
   • Near-synonym: limber
   • Over hill, over dale / As we hit the dusty trail, / And those caissons go rolling along. - 1908, Edmund Louis Gruber, “The Caissons Go Rolling Along”:

   Synonyms: limber

7. A large box to hold ammunition.
8. A chest filled with explosive materials, used like a mine.